The two men in the video are brothers and got from 6-20% burns, but are believed to recover. They also released a statement:

Me and my brother are both fine thank god, I got 16% burns, we were having fun in the car filming a video with the windows closed with laughing gas inside. It smelled funny but we didn’t care and we didn’t give it much attention, then my brother used the lighter which set the gas on fire.